simplify process(handler)

the only filter has a pre and a post function

1 files changed, 22 insertions, 21 deletions

diff --git a/bg/ResponseProcessor.js b/bg/ResponseProcessor.js
index 0340a6f..922ff19 100644
--- a/bg/ResponseProcessor.js
+++ b/bg/ResponseProcessor.js
@@ -2,6 +2,7 @@
 * GNU LibreJS - A browser add-on to block nonfree nontrivial JavaScript.
 *
 * Copyright (C) 2018 Giorgio Maone <giorgio@maone.net>
+* Copyright (C) 2022 Yuchen Pei <id@ypei.org>
 *
 * This file is part of GNU LibreJS.
 *
@@ -24,16 +25,16 @@
   only the "interesting" HTML and script requests and leaving the other alone
 */
 
-let { ResponseMetaData } = require('./ResponseMetaData');
+const { ResponseMetaData } = require('./ResponseMetaData');
 
-let listeners = new WeakMap();
-let webRequestEvent = browser.webRequest.onHeadersReceived;
+const listeners = new WeakMap();
+const webRequestEvent = browser.webRequest.onHeadersReceived;
 
 class ResponseProcessor {
 
   static install(handler, types = ['main_frame', 'sub_frame', 'script']) {
     if (listeners.has(handler)) return false;
-    let listener =
+    const listener =
       async request => await new ResponseTextFilter(request).process(handler);
     listeners.set(handler, listener);
     webRequestEvent.addListener(
@@ -45,7 +46,7 @@ class ResponseProcessor {
   }
 
   static uninstall(handler) {
-    let listener = listeners.get(handler);
+    const listener = listeners.get(handler);
     if (listener) {
       webRequestEvent.removeListener(listener);
     }
@@ -62,8 +63,8 @@ Object.assign(ResponseProcessor, {
 class ResponseTextFilter {
   constructor(request) {
     this.request = request;
-    let { type, statusCode } = request;
-    let md = this.metaData = new ResponseMetaData(request);
+    const { type, statusCode } = request;
+    const md = this.metaData = new ResponseMetaData(request);
     this.canProcess = // we want to process html documents and scripts only
       (statusCode < 300 || statusCode >= 400) && // skip redirections
       !md.disposition && // skip forced downloads
@@ -72,29 +73,29 @@ class ResponseTextFilter {
 
   async process(handler) {
     if (!this.canProcess) return ResponseProcessor.ACCEPT;
-    let { metaData, request } = this;
-    let response = { request, metaData }; // we keep it around allowing callbacks to store state
-    if (typeof handler.pre === 'function') {
-      let res = await handler.pre(response);
-      if (res) return res;
-      if (handler.post) handler = handler.post;
-      if (typeof handler !== 'function') return ResponseProcessor.ACCEPT;
+    const { metaData, request } = this;
+    const response = { request, metaData }; // we keep it around allowing callbacks to store state
+
+    if (typeof handler.pre !== 'function' || typeof handler.post !== 'function') {
+      throw new Error('handler should have a pre and post function.');
     }
+    const res = await handler.pre(response);
+    if (res) return res;
 
-    let { requestId } = request;
-    let filter = browser.webRequest.filterResponseData(requestId);
+    const { requestId } = request;
+    const filter = browser.webRequest.filterResponseData(requestId);
     let buffer = [];
 
     filter.ondata = event => {
       buffer.push(event.data);
     };
 
-    filter.onstop = async unused => {
+    filter.onstop = async _ => {
       // concatenate chunks
-      let size = buffer.reduce((sum, chunk) => sum + chunk.byteLength, 0)
+      const size = buffer.reduce((sum, chunk) => sum + chunk.byteLength, 0)
       let allBytes = new Uint8Array(size);
       let pos = 0;
-      for (let chunk of buffer) {
+      for (const chunk of buffer) {
         allBytes.set(new Uint8Array(chunk), pos);
         pos += chunk.byteLength;
       }
@@ -113,13 +114,13 @@ class ResponseTextFilter {
       }
       let editedText = null;
       try {
-        editedText = await handler(response);
+        editedText = await handler.post(response);
       } catch (e) {
         console.error(e);
       }
       if (editedText !== null && editedText.indexOf('/* LibreJS: script accepted') !== 0) {
         // we changed the content, let's re-encode
-        let encoded = new TextEncoder().encode(editedText);
+        const encoded = new TextEncoder().encode(editedText);
         // pre-pending the UTF-8 BOM will force the charset per HTML 5 specs
         allBytes = new Uint8Array(encoded.byteLength + 3);
         allBytes.set(ResponseMetaData.UTF8BOM, 0); // UTF-8 BOM